Photon emission from slightly roughened tunnel junctions

Abstract

In this paper, we derive expressions for the distribution in angle and frequency of electromagnetic radiation emitted from fluctuations in the tunneling current between two metals separated by a thin oxide barrier. The calculation provides an explicit description of the decoupling of the surface polariton from the surface by virture of small-amplitude roughness present there. In addition, we find radiation from direct coupling of current fluctuations in the junction structure to the transverse radiation field. Numerical calculations are presented which explore the predictions of the theory, when applied to structures similar to those studied experimentally by Lambe and McCarthy. We suggest interpretations of some features of their data, and data reported by Adams, Wyss, and Hansma. The theory indicates that as the amplitude of the roughness is increased, the quantum efficiency of the device should saturate to approach a value independent of the roughness amplitude.